1 / 21

Muscle and Tendon Mechanics, Learning Outcomes

Muscle and Tendon Mechanics, Learning Outcomes. Relationship between muscle force and human strength Numerous influences on skeletal muscle force production capability A few factors that contribute to connective tissue strength. How does muscle force relate to human strength?.

tanyamontes
Download Presentation

Muscle and Tendon Mechanics, Learning Outcomes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Muscle and Tendon Mechanics, Learning Outcomes • Relationship between muscle force and human strength • Numerous influences on skeletal muscle force production capability • A few factors that contribute to connective tissue strength

  2. How does muscle force relate to human strength? What is required to be strong? The ability to develop large joint torque Again, what does joint torque depends on? 1-muscle force, and 2-corresponding moment arm (perpendicular distance) Both of which are heavily influenced by joint angle

  3. Force, Perpendicular Distance, and Torque Muscle Force Perpendicular Distance Muscle Torque

  4. What are some factors that influence skeletal muscle force production? • Cross Sectional Area (CSA) • Muscle Design • Fiber Length • Contraction Velocity • Fiber Type • Neuromuscular Factors

  5. CSA: Hypertrophy or Hyperplasia? • Hypertrophy: • 5% in 6 weeks; 15% in 8 weeks; 9-23% in 3-5 months • Hyperplasia: • Antonio & Gonyea, 1993, and McCall et al., 1996

  6. Muscle Design Muscle design affects skeletal muscle force production Two basic architectures • In-series • In-parallel Pennation angle also affects force production Many muscles exhibit differing combinations of these three characteristics

  7. Muscle Design: In-series In-series fibers are in line one with another Muscle excursion length = fiber excursion length × fiber number Muscle force = average fiber force This arrangement results in greater ranges of motion and movement speeds, and less force

  8. Muscle Design: Parallel Parallel fibers are parallel to one another Muscle excursion length equals fiber excursion length Muscle force equals fiber force × fiber number Facilitates high magnitudes of strength, but usually involves less motion

  9. Muscle Design: Pennation Angle Angle is relative to the long axis of muscle (θ > 0) Muscle shortening length is less than fiber shortening length, & muscle force is less than fiber force However, more fibers in a given volume result in more force; results in lower range of motion, but greater force

  10. Fiber Length ~ resting length resting length Active force partly depends on overlap of actin and myosin filaments; this overlap partly depends on fiber and sarcomere length This related to active force, however, there are also passive structures that can result in muscle force…

  11. Fiber Length Total force developed by a muscle is the sum of active and passive force Peak force is reached at resting, or slightly longer than resting length (~120% of resting) Many muscles reach peak force near the middle of total joint range of motion

  12. Contraction Velocity Muscle force also can depend upon contraction velocity Resistance training increases the isometric load level What does this imply concerning eccentric training? Pros and cons?

  13. Contraction Velocity & Power Maximum power is reached at about 33% of peak force and shortening velocity According to this figure, what is theoretically best when training for power?

  14. Fiber Type At a given speed of shortening, a muscle with more fast-twitch fibers can produce greater force than a muscle with more slow-twitch fibers force  > 50% FT < 50% FT velocity 

  15. Neuromuscular Factors:Firing Rate and Recruitment

  16. Can Pain Also Affect Muscle Force?

  17. Tendon and Ligament Mechanics • Tendon and ligament consist of: • 70% water • 25% collagen • 5% ground substance and elastin • Ligaments have slightly less elastin and are slightly less strong than tendons

  18. Tendon and Ligament Mechanics Arrangement of collagen fibers Tendon: Very stiff and resistant to tensile forces, but not as resistant to compression or shear forces Ligament: Better suited for non-axial loads, yet slightly less able to resist tensile forces

  19. Tendon and Ligament Mechanics These collagen fibers are naturally crimped (wavy)

  20. Tendon and Ligament Mechanics • Small forces result in strain (~10%) that is elastic and rather spring-like • Large forces can result in plastic strain (~20%) • Stiffness depends upon CSA and collagen composition • Tendons and ligaments are both viscoelastic and anisotropic

  21. Stress Relaxation: An Unusual Traits of Most Connective Tissue Strain is constant

More Related